The following warning has appeared when building the release/2.2 branch:

/mnt/resource/j/workspace/dotnet_source-build/release_2.2/CentOS7.1_Release/repos/dir.targets(204,5): warning : Detected package id/version(s) in the cache that were source-built, but contents don't match. They were probably downloaded. See /mnt/resource/j/workspace/dotnet_source-build/release_2.2/CentOS7.1_Release/bin/conflict-report/before-templating/ for usage details. Microsoft.NETCore.ILAsm 2.2.0-preview2-26905-03, Microsoft.NETCore.ILDAsm 2.2.0-preview2-26905-03, Microsoft.NETCore.Jit 2.2.0-preview2-26905-03, Microsoft.NETCore.Runtime.CoreCLR 2.2.0-preview2-26905-03, Newtonsoft.Json 9.0.1 [/mnt/resource/j/workspace/dotnet_source-build/release_2.2/CentOS7.1_Release/repos/templating.proj]

The earliest PR this was detected in was #761, although it could have been introduced earlier, since this was the last CI build available.